ALSA: usb-audio: Fix a missing error check in scarlett gen2 mixer

The check of the returned error code is missing in
scarlett2_update_monitor_other().  Let's fix it.

Fixes: d5bda7e0 ("ALSA: usb-audio: scarlett2: Add support for the talkback feature")
Reported-by: kernel test robot <lkp@intel.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/202109131831.9IodEzRx-lkp@intel.com
Link: https://lore.kernel.org/r/20210929073540.9611-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/mixer_scarlett_gen2.c

@@ -2450,6 +2450,8 @@ static int scarlett2_update_monitor_other(struct usb_mixer_interface *mixer)
 		err = scarlett2_usb_get_config(mixer,
 					       SCARLETT2_CONFIG_TALKBACK_MAP,
 					       1, &bitmap);
+		if (err < 0)
+			return err;
 		for (i = 0; i < num_mixes; i++, bitmap >>= 1)
 			private->talkback_map[i] = bitmap & 1;
 	}